Donald Trump’s immigration paper asserts, as “core principles,” that “there must be a wall across the southern border” because “a nation without borders is not a nation.” And it argues that “any immigration plan must improve jobs, wages, and security for all Americans,” because “a nation that does not serve its own citizens is not a nation.” Many have observed that America has never had a wall across its southern border, and that no immigration plan has ever improved wages and security for all Americans. By Trump’s logic, America has never been a nation.

One wonders what he calls the country that allowed his ancestors to immigrate here.

He is of German stock on his father’s side.

Prior to his grandfather’s arrival, plenty of immigration restrictionists believed, not without reason, that German immigration had irrevocably changed their communities.

As one example, consider what took place in Cincinnati, Ohio.

“In the 1840s and 1850s, Cincinnati society became increasingly unstable as German and Irish immigrants poured in,” The Cincinnati Inquirerreported in a historical retrospective. When an Italian emissary of the Pope visited in 1853, “German Catholics took to the streets armed with guns, pistols, clubs, canes and sling shots trying to run Cardinal Bedini out of town. The Germans, many of whom fled to the U.S. after the failed European revolutions of 1848, saw the priest as a symbol of repression.”

Two years later, Germans clashed with a nativist mob alarmed by a rumor about electoral shenanigans. “German-Americans barricaded streets into Over-the-Rhine on the north edge of the Miami-Erie Canal,” the story notes. “Members of the Turners, a German physical fitness organization, aimed their cannon and ‘shot it over the head of the mob of nativists that came at them,’ says Don Heinrich Tolzmann, University of Cincinnati German-American studies director and curator of UC's German-American Collection.” German immigrants, who started many German language settlements in the U.S., “had become such a force at the ballot box that they pushed for—and received—bilingual education in city schools and Sunday beer sales.”

The Know-Nothing Party ultimately failed at mid-century to stop the immigration of both Irish and Germans. And because they failed, Frederich Christ Trump could immigrate to America in 1885. That decade, 5.2 million immigrants arrived in the U.S., and 3.7 million immigrants arrived the next decade. The unskilled German laborers competed with Americans. The skilled German craftsmen competed with Americans. The German farmers competed with Americans.

Some of the Americans lost jobs or income.

Today, there are nearly 50 million Americans of German ancestry. Many have hazy, romanticized notions of the time when their ancestors came to America. And some, like Trump, champion restrictionist views on immigration that would’ve barred their own grandfathers from coming here had bygone Americans applied them. This despite the fact that, compared to Hispanic immigration today, the waves of 19th-century immigration imposed far higher costs on those already here: Contagious diseases killed more people; those at the bottom of the economic ladder vying with newcomers for work had less of a safety net to fall back on if outcompeted; radical political ideas from abroad led to violent clashes; immigrant riots rocked numerous cities; and every cost was born by a much, much poorer America.

This nation of immigrants will defeat its nativist elements again, as it has periodically throughout its history. It is nevertheless unfortunate that a candidate pledging to make America great again is running against something that made it great in the first place. In the 19th century, as today, immigration created more winners than losers. But no wave of immigrants ever improved “jobs, wages, and security for all Americans.” To mandate that threshold would fundamentally change America.

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Conor Friedersdorf is a California-based staff writer at The Atlantic, where he focuses on politics and national affairs. He is the founding editor of The Best of Journalism, a newsletter devoted to exceptional nonfiction.